This invention relates to novel polyisobutene substituted succinimides and their use as fuel additives.
Hydrocarbon fuels generally contain numerous deposit-forming substances. When used in internal combustion engines, deposits tend to form on and around constricted areas of the engine in contact with the fuel. In diesel engines, deposits tend to accumulate in the fuel injection system, thereby hampering good performance of the engine. In spark ignition engines deposits can build up on engine intake valves leading to progressive restriction of gaseous fuel mixture flow into the combustion chamber and also to valve sticking. It is common practice therefore to incorporate a detergent in the fuel composition for the purpose of inhibiting the formation, and facilitating the removal, of engine deposits, thereby improving engine performance.
Many different types of compounds are known as detergents for fuels. Typical examples include polyisobutene-substituted (PiB) succinimides such as those disclosed in EP-A-565285, where the amine portion is derived from a polyalkylene amine.
JP-A-07278142 discloses that the reaction product of an imidazoline and a PiB succinic acid is useful as a dispersant in compositions which are used as lubricants for gasoline.
It has now been discovered the novel PiB succinimides of this invention are effective detergents for use in fuels.
This invention relates to a compound represented by the formula 
wherein in formula (I): R is a polyisobutene group; R1, R2 and R3 are each independently hydrogen, alkyl groups of 1 to 18 carbon atoms, cycloalkyl groups of 4 to 10 carbon atoms or aryl groups of 6 to 10 carbon atoms; and n is an integer of 0 to 4. The invention also relates to an additive package for use in making fuels comprising the foregoing compound. The invention relates to fuel compositions containing the foregoing compound.
The novel compounds of the invention are compounds represented by the formula 
wherein in formula (I): R is a polyisobutene (PiB) group; R1, R2 and R3 are each independently hydrogen alkyl groups of 1 to 18 carbon atoms, cycloalkyl groups of 4 to 10 carbon atoms, or aryl groups of 6 to 10 carbon atoms; and n is an integer of from 0 to 4. In one embodiment, R1, R2 and R3 are each H. In one embodiment, n is 1 to 4, and in one embodiment n is 3.
In one embodiment, the polyisobutene group R is derived from a xe2x80x9chigh reactivexe2x80x9d PiB. PiBs in which at least 70% of the terminal olefinic double bonds are of the vinylidene type are commonly known as xe2x80x9chigh reactivexe2x80x9d polyisobutenes, as distinguished from xe2x80x9clow reactivexe2x80x9d PiBs having a lower proportion of vinylidene terminal double bonds. In one embodiment, at least 80% of the terminal olefinic double bonds are of the vinylidene type, and in one embodiment at least 90% are of the vinylidene type. Examples of xe2x80x9chigh reactivexe2x80x9d polyisobutenes include Ultravis(copyright) marketed by BP Chemicals and Glissopal(copyright) marketed by BASF.
Preferably the PiB has a number average molecular weight of from 700 to 2500, and in one embodiment from 750 to 1500.
In one embodiment, the compounds of the invention may be made by reacting a PiB-substituted succinic acylating agent such a polyisobutene succinic anhydride (PiBSA) with aminopropylimidazole. Methods for making PiB-substituted succinic acylating agents are well known in the art; examples are disclosed in EP-A-565285 and EP-A-623631. In one embodiment, the compounds are made by reacting the acylating agent with aminopropylimidazole in the presence of a solvent. The solvent can be an aromatic or aliphatic hydrocarbon solvent.
In one embodiment, the invention provides for a fuel composition comprising a major amount of a hydrocarbon fuel, and from 10 to 1000 parts per million (ppm) based on the total weight of the fuel composition of foregoing compound of the invention. In one embodiment, the compound of the invention is added to the fuel as part of an additive package, the package being added to the fuel at concentrations of from 200 to 3000 ppm, and in one embodiment from 600 to 1000 ppm. Thus another aspect of the invention provides an additive package for fuel compositions, comprising from 5 to 30% by weight of the inventive compound, a carrier fluid, and optionally a solvent, preferably an aromatic or aliphatic hydrocarbon solvent. Suitable carrier fluids include alkyl phenols, optionally alkoxylated; esters of acids/alcohols, acids/polyols or acids/glycol ethers, the acids being saturated or unsaturated; phthalate esters; trimellitate esters; alkoxylated alcohols or polyols; polyalkylene glycols; and lubricating oils. Suitable solvents may include most known aromatic or aliphatic hydrocarbons or glycol ethers. The invention also comprises in a still further aspect the use of the inventive compounds or additive packages as detergents in hydrocarbon fuels.
In one embodiment, the hydrocarbon fuel comprises a hydrocarbon fraction boiling in the gasoline range or a hydrocarbon fraction boiling in the diesel range. Gasolines suitable for use in spark ignition or gasoline engines, e.g. automobile engines, generally boil in the range from 30xc2x0 C. to 230xc2x0 C. Such gasolines may comprise mixtures of saturated, olefinic and aromatic hydrocarbons. They may be derived from straight-run gasoline, synthetically produced aromatic hydrocarbon mixtures, thermally or catalytically cracked hydrocarbon feedstocks, hydrocracked petroleum fractions or catalytically reformed hydrocarbons. The octane number of the base fuel is not critical and will generally be above 65. In the gasoline, hydrocarbons may be replaced in part by alcohols, ethers, ketones or esters, typically in an amount up to 20% by weight. Alternatively, as the liquid hydrocarbon fuel there may be used any fuel suitable for operating spark compression or diesel engines, such as those which may be found in road vehicles, ships and the like. Generally, such a diesel fuel will boil in the range from about 140xc2x0 C. to about 400xc2x0 C. (at atmospheric pressure), particularly in the range from about 150xc2x0 C. to 390xc2x0 C., especially from about 175xc2x0 C. to 370xc2x0 C. Such fuels may be obtained directly from crude oil (straight-run) or from a catalytically or thermally cracked product or a hydrotreated product, or from a mixture of the aforesaid. Alternatively there may be used a biofuel, for example rape seed methyl ester. The cetane number will typically be in the range from 25 to 60.
In one embodiment, the fuel composition contains the compound of formula (I) in an amount sufficient to provide dispersancy. Typically in a gasoline fuel this amount is in the range from 20 to 1000 ppm w/w based on the total weight of the composition. Typically in a diesel fuel this amount is in the range from 10 to 500 ppm w/w based on the total weight of the composition.
The fuel composition may be prepared by blending a concentrate composition comprising a fuel compatible hydrocarbon solvent and the compound of formula (I) with the hydrocarbon fuel.
The fuel composition may contain in addition to the compound of formula (I) known fuel additives. The nature of the additives depend to some extent on the end-use of the fuel composition. Diesel fuel compositions may contain nitrates or nitrites as a cetane improvers, or copolymers of ethylene and/or vinylesters, e.g. vinylacetate, as pour point depressants. Gasoline fuel compositions may contain a lead compound as an anti-knock additive and/or an antioxidant, e.g. 2,6-di-tert-butyl phenol, and/or an anti-knock compound other than a lead compound, and/or an additional dispersant, for example a PIB polyamine. The other additives (if any) may be blended directly into the fuel composition or may be incorporated by way of a concentrate composition.
The compounds of the invention are useful as thermal stabilisers for jet fuels. In high speed aircraft, both civilian and military, the liquid fuel is combusted to produce power, but also is circulated in the aircraft as a heat exchange fluid to remove the excess heat generated at such speeds e.g. in lubricating oils. The fuel is thus maintained for long periods at high temperatures, which results in discoloration and/or decomposition to produce soluble coloured products and/or insoluble products such as gums, sediments and granular material. Insoluble products can form deposits that reduce the heat exchange capacity and can block filters potentially causing loss of power. Soluble coloured by-products are unsightly and an indication of some decomposition. The cause of discoloration and/or decomposition may be from phenols, naphthenates and sulphur compounds and/or metals which are often present in the fuels. The compounds of the present invention reduce or prevent this discoloration and/or decomposition when added to jet fuels. Accordingly another aspect is the use of the compound of the invention to reduce or prevent discoloration and/or decomposition upon heating of jet fuels. Jet fuels containing the compound of formula (I) have an improved thermal stability as shown by a reduced tendency to discolor and/or produce solids on heating compared to the fuel alone in the isothermal corrosion and oxidation test (ICOT based on ASTM D4871).
In one embodiment, the compound of the inveniton is present in the jet fuel in amount of at least 1 ppm, and in one embodiment 1 to 1000 ppm, and in one embodiment 5 to 500 ppm, and in one embodiment 10 to 100 ppm; based on the total weight of the jet fuel composition. The compound may be mixed with the jet fuel in the form of a concentrate, e.g. in an aliphatic aromatic hydrocarbon solvent at 20 to 80% by weight of said compound, or it may be added neat to the jet fuel.
Jet fuel itself is a middle boiling distillate, usually kerosene which may be mixed with gasoline and optionally light petroleum distillate as in mixtures of gasoline and kerosene or light petroleum distillate, e.g. in weight amounts of 20-80:80-20 such as 50-75:50-25. The fuels for military use are designated JP4 to JP 8:e.g. JP4 as 65% gasoline/35% light petroleum distillate (according to US Mil. Spec. MIL 5624G). JP5 is similar to JP4 but of higher flash point. JP7 is a high flash point special kerosene for advanced supersonic aircraft. JP8 is a kerosene similar to Jet A1 (according to MIL 83133C). Jet fuel for civilian use is usually a kerosene type fuel and designated Jet A or Jet A1. The jet fuel may have a boiling point of 65-350xc2x0 C. or 65-320xc2x0 C., initial boiling point of 150-220xc2x0 C., e.g. 200xc2x0 C., a 50% boiling point of 220-320xc2x0 C. and a 90% boiling point of 260-350xc2x0 C., and API Gravity of 30-40. Jet fuels for turbojet use may boil at 90-260xc2x0 C. (ASTM D1655-59T). Further details on aviation fuels may be obtained from xe2x80x9cHandbook of Aviation Fuel Propertiesxe2x80x9d, Coordinating Research Council Inc., CRC Report No. 530 (Society of Automotive Engineers Inc., Warrendale, Pa., USA, 1983) and on US military fuels, from xe2x80x9cMilitary Specification for Aviation Turbine Fuelsxe2x80x9d, MIL-T-5624P.
The jet fuel may be a straight run kerosene optionally with added gasoline, which preferably is purified to reduce its content of components contributing to, or encouraging formation of colored products and/or precipitates. Among such components are aromatics, olefins and mercaptans. Thus the fuels may be purified to reduce their mercaptan content, e.g Merox fuels and copper sweetened fuels, or to reduce their sulphur content, e.g. hydrofined fuels or Merifined fuels. Merox fuels are made by oxidation of the mercaptans and have a low mercaptan S content (e.g. less than 0.005% wt S, and in one embodiment 0.0001-0.005% wt. S) but a higher disulphide S content (e.g. up to 0.4% wt S, and in one embodiment up to 0.3% wt S, and in one embodiment 0.05 to 2%, and in one embodiment 0.05 to 0.25%); their aromatic (e.g. phenolics) and olefins content are hardly changed. Hydrofined jet fuels are ones in which the original fuel has been hydrogenated to remove at least some of the sulphur compounds, e.g. thiols, and under severe conditions to saturate the aromatics and olefins; hydrofined jet fuels have very low sulphur contents (e.g. less than 0.01 % S by weight). Merifined fuels are fuels that have been extracted with an organic extractant to reduce or remove their contents of sulphur compounds and/or phenols. The jet fuel may also contain metals, either following contact with metal pipes or carried over from the crude oil; examples of such metals are copper, nickel, iron and chromium usually in amounts of less than 1 ppm, e.g. each in the 10-150 parts per billion (ppb) concentration range. Merox and hydrofined fuels are preferred and may be used in JP4 to JP8 jet fuels.